The prompt localizations of GRBs provided by the Swift satellite have enabled major advances in our understandings of GRB prompt and afterglow emission. The Swift BAT detects about 100 GRBs per year and provides positions accurate to better than 3 arcminutes within tens of seconds, while the XRT detects about 95 afterglows per year and provides positions accurate to a few arcseconds within a minute or two of the GRB onset. Here I review highlights of the Swift mission, including X‐ray light curves, localization of short GRBs, and ambiguities in the classification of GRBs.

I summarize the prompt spectral
characteristics of X‐ray flashes (XRFs) using the available spectral parameters of the BATSE, the Beppo
the
‐2, and the Swift gamma‐ray bursts (GRBs). The spectral properties of XRFs are similar to those of classical GRBs (C‐GRBs) except the
energy and the fluence of XRFs are much smaller. The fluence ratio distribution from XRFs to C‐GRBs forms a continuum. This systematic study of the spectral properties of XRFs and C‐GRBs tightens an evidence that these bursts arise from the same phenomenon.

We summarise the X‐ray temporal and spectral variability properties of GRBs as observed using the Swift
satellite. Despite much individual complexity, the flux and spectral variability can be reasonably well described by a combination of two components—which we denote as the prompt and the afterglow. The first, prompt component consists of the burst and its initial decay while the second, afterglow component fits the X‐ray plateau phase and subsequent decline observed in the majority of GRBs. When strong spectral variability occurs it is associated with the prompt component while the X‐ray plateau and later emission shows little if any spectral variability. We briefly compare the observations with some of the proposed models. Any model for the early or late emission must explain the differences in both temporal and spectral behaviour.

The flare activity that is observed in GRBs soon after the prompt emission with the XRT (0.3–10 KeV) instrument on Board of the Swift satellite is leading to important clues in relation to the physical characteristics of the mechanism generating the emission of energy in Gamma Ray Bursts. We will briefly refer to the results obtained with the recent analysis [1] and [2] and discuss the preliminary results we obtained with a new larger sample of GRBs [limited to early flares] based on fitting of the flares using the Norris 2005 profile. We find, in agreement with previous results, that XRT flares follow the main characteristics observed in [3] for the prompt emission spikes. The estimate of the flare energy for the subsample with redshift is rather robust and an attempt is made, using the redshisft sample, to estimate how the energy emitted in flares depends on time. We used a
cosmology.

A comprehensive analysis of the X‐ray afterglows of GRBs from the early shallow decay to late jet like decay phases observed with Swift/XRT is presented. We find that no significant spectral evolution is observed from the shallow to normal decay segments in the XRT lightcurves, and the normal decay segment is roughly consistent with external‐shock models, favoring the idea that the shallow decay segment may be due to long‐lasted refreshed shocks, but the observed chromatic breaks in the X‐ray and optical bands of some bursts raise concerns for this scenario. GRBs 060413, 060522, 060607A, and 070110 are four significant outliers of this scenario in our sample, and they likely have an internal origin, which demands continuous operation of a long‐term central engine. In order to explore the late jet‐like breaks in the afterglow light curves we analyze the Swift XRT data for 179 GRBs and the optical afterglow data for 57 pre‐ and post‐Swift GRBs. We find that no textbook version of jet break is found, in which the data fully satisfy jet break criteria. By relaxing one or more requirements, candidates to various degrees are identified. The break time in the X‐ray band is earlier than that in the optical bands, and among thirteen bursts having both the optical and X‐ray light curves, only seven have an achromatic break. Even in these cases only one band data satisfies the closure relations. These are great issues to interpret these candidates as jet breaks and further inferring GRB energetics.

One of the most interesting discoveries of the Swift mission is the wide variety of X‐ray behaviors observed in the early GRB afterglows. We selected a large sample of bright X‐ray flares observed by XRT up to March 2008. The Norris et al. (2005) profile was adopted to characterize the morphological and timing properties of the flares in different energy bands, such as the peak, rise and decay times, the width and the asymmetry of each flare. These parameters were used to estimate other properties in a homogeneous way, such as the temporal lag between the same pulse seen at different energy bands, or the width of the flare as a function of energy, thus allowing us to derive important clues on the underlying physical mechanism and the connections with the central engine.

In this paper we make an attempt to combine the two kinds of data from the Swift‐XRT instrument (windowed timing and photon counting modes) and the from BAT. A thorough desription of the applied procedure will be given. We apply various binning techniques to the different data: Bayes blocks, exponential binning and signal‐to‐noise type of binning. We present a handful of lightcurves and some possible applications.

Preliminary results of our analysis on the extended emission of short/medium duration GRBs observed with Swift/BAT are presented. The Bayesian blocks algorithm is used to analyze the burst durations and the temporal structure of the lightcurves in different energy bands. We show here the results of three bursts (GRBs 050724, 061006 and 070714B) that have a prominent soft extended emission component in our sample. The extended emission of these bursts is a continuous, flickering‐liked component, lasting
post the GRB trigger at 15–25 keV bands. Without considering this component, the three bursts are classified as short GRBs, with
GRB 060614 has an emission component similar to the extended emission, but this component has pulse‐liked structure, possibly indicating that this emission component is different from that observed in GRBs 050724, 061006, and 070714B. Further analysis on the spectral evolution behavior of the extended emission component is on going.

The entropic scale index δ is independent of artificial selection effects and reflects the genuine of the variation of a GRB lightcurve. With the current redshift‐known GRB sample, we find a tight
relation and a tentative correlation between
and δ for typical GRBs. Two low‐luminosity GRBs, 980425 and 060218, are significant outliers of the
relation (in 3σ confidence level), likely favoring the idea that they are of a unique GRB population.

It is recently suggested that low‐luminosity gamma‐ray bursts (LL‐GRBs) are likely a unique GRB population. We present a systematical analysis of the light‐curve characteristics from X‐ray to gamma‐ray bands for two prototypical LL‐GRBs, 980425 and 060218. It is found that both the pulse width (w) and the ratio of the rising width to the decaying width
of the two bursts are energy‐dependent over a broad energy band. There exists a significant trend that the pulses tend to be narrower and more symmetrical at higher energy bands for the two events. Both the X‐rays and gamma‐rays follow the same
and
relations. These facts may indicate that the X‐ray emission tracks the gamma‐ray emission, and both are likely to originate from the same physical mechanism. Their light curves show significant spectral lags. We calculate the three types of lags with the pulse peaking time
the pulse centroid time
and the cross‐correlation function (CCF). The lag calculated by CCF is strongly correlated with that derived from
but the lag derived from
is less correlated with that derived from
and CCF. We also find that their pulse temporal characteristics are normal when compared to the other normal BATSE GRB pulses, indicating that GRBs 980425 and 060218 may share a similar radiation physics with them.

We select a sample including 42 individual tracking pulses (here we defined tracking as the cases in which the hardness follows the same pattern as the flux or count rate time profile) within 36 Gamma‐ray Bursts (GRBs) to investigate the spectral hardness,
evolutionary characteristics. It is found that the overall characteristics of
of our selected sample are: 1) the
evolution in the rise phase always start on the high state (the values of
are always higher than 50 keV); 2) the spectra of rise phase clearly start at higher energy (the median of
are about 300 keV), whereas the spectra of decay phase end at much lower energy (the median of
are about 200 keV); 3) the spectra of rise phase are harder than that of the decay phase and the duration of rise phase are much shorter than that of decay phase as well. In other words, for a complete pulse the initial
is higher than the final one and the duration of initial phase (rise phase) are much shorter than the final phase (decay phase).

We report on observations of correlated behavior between the prompt γ‐ray and optical emission from GRB 080319B, which (i) strongly suggest that they occurred within the same astrophysical source region and (ii) indicate that their respective radiation mechanisms were most likely dynamically coupled. Our preliminary results, based upon a new cross‐correlation function (CCF) methodology for determining the time‐resolved
spectral lag, are summarized as follows. First, the evolution in the arrival offset of prompt γ‐ray photon counts between Swift‐BAT 15–25 keV and 50–100 keV energy bands (intrinsic γ‐ray spectral lag) appears to be anti‐correlated with the arrival offset between prompt 15–350 keV γ‐rays and the optical emission observed by TORTORA (extrinsic γ‐ray/optical lag), thus effectively partitioning the burst into two main episodes at
Second, prompt optical emission is nested within intervals of both (a) trivial intrinsic γ‐ray spectral lag (
and
) with (b) discontinuities in the hard to soft evolution of the photon index for a power law fit to 15–150 keV Swift‐BAT data (
and
), both of which coincide with the rise
and decline
of prompt optical emission. This potential discovery, robust across heuristic permutations of BAT energy channels and varying temporal bin resolution, provides the first observational evidence for an implicit connection between spectral lag and the dynamics of shocks in the context of canonical fireball phenomenology.

An analysis of the prompt gamma‐rays of the X‐ray flashes (XRFs) observed with the Burst Alert Telescope (BAT) on board Swift
satellite is presented. A division line of
(roughly corresponding to a peak energy of the
spectrum of
) is adopted to separate XRFs and typical gamma‐ray bursts(GRBs), where Γ is the power law index of the BAT spectrum. Among 235 bursts detected with BAT, the detection ratio of XRFs to GRBs is 42:193, consistent with the observations of
‐2. The distribution of Γ for the entire set of the GRBs/XRFs is a normal distribution without featuring the GRBs and XRFs as two distinct groups. By comparing the gamma‐ray fluences and the peak fluxes in different energy bands, it is found that the XRFs are globally softer than the GRBs, but during the peak time the spectra of both the GRBs and the XRF are similar, illustrating that the dominated radiation mechanisms are similar. These results support that XRFs are natural extensions of GRBs into the soft band.

Two classes of gamma‐ray bursts have been identified in the BATSE catalogs characterized by durations shorter and longer than about 2 seconds. There are, however, some indications for the existence of a third type of burst. Swift satellite detectors have different spectral sensitivity than pre‐Swift ones for gamma‐ray bursts. Therefore it is worth to reanalyze the durations and their distribution and also the classification of GRBs. Using The First BAT Catalog the maximum likelihood estimation was used to analyzed the duration distribution of GRBs. The three log‐normal fit is significantly (99.54% probability) better than the two for the duration distribution. Monte‐Carlo simulations also confirm this probability (99.2%).

A sample of 286 gamma‐ray bursts (GRBs) detected by the Swift satellite and 358 GRBs detected by the RHESSI satellite are studied statistically. Previously published articles, based on the BATSE GRB Catalog, claimed the existence of an intermediate subgroup of GRBs with respect to duration. We use the statistical
test and the F‐test to compare the number of GRB subgroups in our databases with the earlier BATSE results. Similarly to the BATSE database, the short and long subgroups are well detected in the Swift and RHESSI data. However, contrary to the BATSE data, we have not found a statistically significant intermediate subgroup in either Swift or RHESSI data.

In this work we analyse
statistical properties of 82 long‐GRBs with confirmed redshift and well‐sampled light curves observed in R‐band. The data gathered here show a cosmological evolution trend on various intrinsic GRB features. In particular, we find that the optical burst duration, the isotropic optical luminosity at the observed maximum and the time‐integrated isotropic energy are all redshift dependent. The lack of correlations between the redshift and the observational GRB quantities (i.e. optical fluence and observed peak flux) points out that the detected trends are not affect by significant selection effects. This fact suggests that the intrinsic optical afterglow luminosity follows the cosmological evolution of a circumburst environment which determines the optical afterglow luminosity rate. It is interesting to note that the similar analysis performed for the main parameters of the gamma‐ray emission show no evidence for a hypothetical redshift‐dependent effect according to which the characteristics of a GRB‐event depend on its location in the universe. Furthermore, there are correlations between the luminosity, the total energy and the duration of the gamma‐ray and optical emission separately, which can arise from universal features of the observed lightcurves.

The Swift Ultra‐Violet/Optical Telescope has observed
gamma‐ray bursts (GRBs) in its first two‐and‐a‐half years of operation. From this collection of observations we have obtained
well sampled light curves. Using this dataset we present general optical/UV properties of GRBs, including filter dependent temporal slopes and color‐color relationships. We also show that correlations exist between both the 11 hour X‐ray flux (0.3–10 keV) and the prompt gamma‐ray fluence (15–150 keV) and the v‐band magnitude at 2000 s.

The precise localization of short/hard (Type I) gamma‐ray bursts (GRBs) in recent years has answered many questions but raised even more. I present some results of a systematic study of the optical afterglows of long/soft (Type II) and short/hard (Type I) GRBs, focusing on the optical luminosity as another puzzle piece in the classification of GRBs.